1. Field of the Invention
This invention relates generally to the field of geologic mapping of sedimentary bodies on the earth's surface. More specifically, the invention relates to techniques for identifying sedimentary bodies and patterns using aerial or space-based images.
2. Background Art
Exploration for minerals, including petroleum, includes as one of several initial tasks identifying geographic areas of the earth in which accumulations of geologically prospective materials is likely. Particularly in petroleum exploration, the geologically prospective materials include sediments.
Sediments are produced, among other ways, by the action of wind and water on the surface of the earth. Wind and water tend to erode materials from the elevated features and carry them some distance related to the distance at which the erosive agent (wind or water) moves and on the particle size of the materials actually moved from upland areas. Sediments may then be deposited at other places on the earth's surface by any one of a number of processes. Accumulations of sediment typically take place in localized depressions on the earth's surface known as “basins.”
Exploration techniques known in the art include structural mapping of surface exposures (“outcrops”) of sediments, mapping features on the earth's surface, reflection seismography of structures disposed under the earth's surface, gravitometry (measurement of local acceleration of earth's gravity) mapping, mapping of the earth's local magnetic field, and magnetotelluric (mapping of local electromagnetic fields generated by electromagnetic radiation from space) mapping, among others. These exploration techniques are intended, among other purposes, to identify, within accumulations of sediment, locations where mineral bearing structures are most likely to be found. Many sediment accumulations commonly occur within basins. After identification of accumulations of sediment, the localized structural and stratigraphic mapping techniques, including, for example, seismic mapping and seismic stratigraphy, can be used to more precisely evaluate the likelihood of the presence of suitable sediment compositions and suitable geologic structures in which minerals may be found.
Exploration techniques known in the art, particularly those used in petroleum exploration, rely to a great extent on identification of areas where rivers deposited sediment in coastal areas, in order to locate substantial sediment accumulations. These deposits in coastal areas may be associated with currently active rivers, for example, sediment deposits in the Gulf of Mexico near the mouth of the Mississippi River, or they may be in geologic areas believed to have been associated with coastal sediment deposition in the past. The exploration techniques known in the art, however, can be time consuming and expensive, and may ultimately fail to identify certain very large sediment accumulations in non-coastal areas because of practical limitations on the scale at which techniques known in the art can be performed. It is therefore desirable to provide exploration techniques which can enable quick evaluation of large areas of the earth's surface, and which may identify previously unknown sediment accumulations.